Silanes are used for building protection as anti-corrosives, anti-graffiti-agents and water-repellents on substrates such as marble, sandstone, concrete, granite, sand-limestone, terracotta, clinker, split-face block or bricks. For such applications, the treatment products need to be preferably water-based and slightly acidic.
Fluorinated silanes exhibit the best performance with regard to simultaneous water-repellence and oil-repellence. Such fluorinated silanes so far possess several drawbacks. First of all, they do not easily form stable solutions, emulsions or dispersions with solvents having a dielectric constant greater than 30 at 20° C. Secondly, most of the fluorinated silanes used for building protection may release perfluoro-octanoic acid (PFOA), which has been found to persist and bioaccumulate in animal and human tissue and to accumulate in the liver where it inhibits glutathione peroxidase, a selenoprotein essential for thyroid hormone conversion, thereby also causing cancer (Occup Environ Med 60(10):722-9 (2003); Int J Cancer 78(4):491-5 (1998)).
U.S. Pat. No. 6,054,601 A discloses compositions of long-chain perfluorinated silanes and aminosilanes that undergo a reaction in aqueous media.
EP 0738771 A1 discloses aqueous compositions comprising long-chain perfluorinated silanes and aminosilanes. Compositions comprising less than 90% water are described to possess shelf instability.
U.S. Pat. No. 5,442,011 A discloses compositions of long-chain perfluorinated silanes and aminosilanes that undergo a reaction in aqueous media.